Centrifugal braking and control apparatus



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A rromw/S United States Patent 6 CENTRIFUGAL ERAKENG AND CONTROL APPARATUS Richard I. Huser, Mount Healthy, and Anthony H. Stuhlreyer, Silver-ton, Ohio, assignors to The Western States Machine Company, Hamilton, Ohio, a corporation of Utah Original application lune 21, 1947, Serial No. 756,308. Divided and this application November 1, 1952, Serial No. 318,258

5 Claims. (Cl. 138-405) This invention relates to an apparatus for the control of centrifugal machines such as the type used in sugar refineries, and is especially concerned with the brake setting apparatus and control of the cycle of operation of the centrifugal.

This application is a division of our copending application, Serial No. 756,308, filed June 21, 1947, now abandoned.

In the operation of heavy high speed centrifugals such as employed in the sugar industry, the centrifugals may be driven by electric motors, these motors usually being of the alternating current polyphase induction type. The motors can be connected directly to the centrifugal, or there may be a fluid coupling between the motor and the centrifugal basket.

One use of a heavy high speed centrifugal in the sugar industry is for the centrifugal separation of a syrup from the sugar. The massecuite or magma is loaded into the centrifugal and then the basket is brought up to the desired operating speed for centrifuging. During the centrifuging, an operation such as a washing of the separated sugar remaining in the basket can be carried out. At the end of the centrifuging operation, arrangements are provided whereby the centrifugal can be operated at a low speed for removal of the separated sugar from the basket. The loaded basket is accelerated to running speed in an extremely short period, the complete cycle being as short as two minutes or less, andthe cycles of operation are frequently repeated. The drive shaft connecting the motor and the basket usually is provided with a braking apparatus for the purpose of bringing the basket to a stop or slowing the same when desired.

One of the objects of the invention is to provide an improved organization of a centrifugal machine having an automatic cycle control including automatic and manually controlled braking apparatus wherein the manual E braking control will be held in a brake-on position when the brake is manually applied, application of the'manual braking means serving to stop the automatic cycle control if the automatic braking portion thereof has not commenced.

Another of the objects of the invention is to provide an improved organization of centrifugal apparatus automatic cycle control wherein new combinations of timer centrifugal apparatus to which the invention can be applied. i

Fig. 2 is an enlarged fragmentary view, partially in ice section, of a mechanical brake lever operating system wherein an air or hydraulic cylinderis used to operate the brake.

Fig. 3 is a fragmentary elevation of the apparatus shown in Fig. 2. l

Fig. 4 is a fragmentary plan view showing a portion of the apparatus of Fig. 2 with the brake in the hand applied and locked position.

Fig. 5 is an enlarged fragmentary view taken along the line 5--5 of Fig. 1 showing details of the brake band expanding and contracting mechanism.

Fig. 6 is a fragmentary plan view of a modification of the invention wherein automatic setting of the brake is accomplished by means of a torque motor instead of the hydraulic actuator shown in detail in Figs. 2 to 4, inclusive.

Fig. 7 is a fragmentary elevation of the apparatus of Fig. 6.

Fig. 8 is a schematic wiring diagram of one circuit that may be used in carrying out the invention.

Fig. 9 is a diagrammatic view of the face of a control timer suitable for use in the circuit of Fig. 8.

Fig. 10 is a diagrammatic view of the face of a process timer suitable for use in the circuit of Fig. 8.

Fig. 11 is a chart showing one example of a time cycle of operation that may be employed with a sugar centrifugal.

In centrifugal apparatus of the type to which the present invention may be applied, an electric motor drives a suspended rotatable gyratory basket, and a brake drum and brake shoes are provided for bringing the basket to a stop after a centrifuging operation has been completed. As mentioned previously, the electric motor may be directly connected to the centrifugal or may be connected through a fluid coupling. The basket is normally surrounded by a casing wherein the expelled liquid may be collected. In operation of the system, the massecuite or magma containing the sugar normally is loaded into the basket as the basket is revolved at slow speed. Following loading of the basket, the electric motor has its speed increased up to that desirable for centrifuging or the fluid coupling is energized; The centrifugal operation drives the syrup from the massecuite .or magma through the basket walls into the casing where it is collected. At an appropriate time during the centrifuging operation, a wash water spray may be operated so as to wash any remaining syrup from the sugar crystals of the walled-up sugar, and this water is expelled centrifugally from the basket. During the centrifuging period, water may be introduced into the brake drum to cool the same. Upon completion of the centrifuging, the electric motor may be connected so as to be used as a regenerative brake during the first part of the slowing down of the basket, and then at a suitable time the regenerativebraking action may be discontinued and a mechanical brake applied. Upon completion of centrifuging, a discharger apparatus can be inserted into the basket, and the basket brought up to a slow speed by means of a jog switch so as to revolve the basket as the discharger scrapes the sugar from the walls of the basket.

It is desirable to be able to set the mechanical brake by hand independently of the power actuator of the automatic cycle control apparatus and to have the hand brake automatically lock itself in place in the brake applied or on" position. When the hand brake is operated for an emergency stop, or for any purpose, the electric power to the driving motor must be interrupted and the automatic control apparatus should be stopped so as to prevent further operation of the centrifugal after the hand brake has been set. v

Referring to Fig. 1, electric motor 20, such as a polyphase induction motor, is employed to drive the suspended rotatable gyratory basket 21 through shaft 22, the motor of Fig. 1 being connected to basket 21 through said shaft 22. Casing 26 collects the centrifugally expelled liquid and may take various forms, such as, for example, the form shown in the patent to Roberts, No. 2,145,633. Brake drum 23 (Figs. 1 and has a pair of brake bands 24, said brake bands being operable by means of apparatus attached to arm 25 in a manner that will be described hereafter. The brake bands are pivoted at 28 (Fig. 1), said pivot being carried by bracket 29 attached to the frame of the machine. The brake bands are contracted or expanded relative to brake drum 23 by rotation of brake band operating shaft 30, said shaft being mounted in bracket 31. Mounted on pins 32 and 33 at the bottom of brake band operating shaft are a pair of brake band operating plungers 34, said plungers having adjusting nuts 35 mounted on one end thereof and with motion limiting collars 36 thereon. Brake drum operating plungers 37 are slidably carried in pivoted cylinders 38, springs 39 being mounted between plungers 37 and the interior closed end walls of cylinders 38 for the purpose of normally urging said plungers outwardly from the base of said cylinder, the collars 36 serving to limit the outward movement of the plungers. Cylinders 38 are pivotally mounted at 40 to the brake drum brackets 41. When the shaft 30 is rotated in a counter-clockwise direction (Fig. 5), the brake drum operating plungers 34 will be moved so as to compress springs 39 and move the brackets 41 toward each other thereby causing the brake bands 24 to tightly engage the brake drum 23, the springs 39 serving to equalize the force on the bands and thus to apply equal pressure on each band.

in one embodiment of the invention, the brake operating shaft 30 may be rotated or operated by an air cylinder. Referring to Fig. 2, shaft 30 has non-rotatably mounted thereon a double arm member 42. Arm 43 thereof is pivotally connected at 44 to piston 45, said piston being slidable within air cylinder 45'. The air cylinder 45' is pivotally mounted at 46 to a suitable bracket (not shown) carried by the frame of the machine. When air or fluid is admitted to chamber 47 of the air cylinder 45, spring 48 will have the force exerted thereby overcome so that piston 45 will move outwardly relative to the cylinder to rotate double arm member 42 in a counter-clockwise direction, thus turning shaft 30 and causing the brake bands to be contracted to set the brake. The second arm 49 of the double arm member 42 will move away from roller 50 of the hand brake operating arm 52 when the air piston operates the brake and thus arm 42 operates independently of the hand setting apparatus, roller 50 being mounted on hand operating arm 52. As will be described hereafter, the admission of air to cylinder 45' may be automatically controlled by the control system although, of course, it may be controlled manually.

When it is desired to set the brake by hand in an emergency, or otherwise, hand operating arm 52 is turned clockwise (Fig. 2) by grasping handle 51 thereof. Hand operating arm 52 pivotally mounted on shaft 53 is held in bracket 54, bracket 54 in turn being mounted on the frame of the machine in some suitable manner. The arm 52 may be keyed to the shaft 53, shaft 53 in turn being rotatable in bracket 54. Also, shaft 53 may be st.- tionary in bracket 54 and the arm 52 rotatable thereon. Upon rotation of the hand operating arm 52, roller 50 will move therewith and will contact or engage the hooked second arm 49 of the double arm member 42 along the inside thereof causing rotation of arm 43 and shaft 30 therewith to set the brake. A complete brake setting movement of handle 51 will result in the parts taking the position shown in Fig. 4 wherein roller 50 engages hooked end 54 of the second arm 49. The center 50 (Fig. 4) and contact point of roller 50 with the surface 49' of the arm 49 has passed beyond the line AA perpendicular to surface 49' and intersecting the center of pivot 53.

Thus it is apparent that the roller 50 has passed beyond the dead center line AA. The hook 54' will limit the movement of roller 50 beyond the dead center position, and thus the brake will be locked in a brake-on position. The hand operating arm 52 is seen to be loosely contactable with arm 49. Spring 48 normally tends to turn arm 42 in a clockwise direction and thus to hold the roller against hook 54. To release the hand brake, it is merely necessary to grasp the handle and recross the dead center line, whereupon spring 48 will return the mechanism to a brake-off position.

The hand operating arm 52 has a sector 55 with a depending cam 56, said cam extending from point 57 around a substantial portion of the are of said sector. The cam is arranged to cooperate with a roller 58, or other suitable switch operator, mounted on switch 59. When the handle 51 is turned to set the brake, cam 56 will immediately, upon movement of said handle, contact roller 58 to operate switch 59, the operation of said switch 59 being employed to interrupt the action of the automatic control apparatus and/or reset the same as desired.

Instead of the air cylinder just described, a torque motor (Figs. 1, 6, 7) may be used to automatically set the brake, a torque motor being one which is constructed to give a limited twist to the operating shaft thereof when power is applied. Torque motor 60 may be mounted on the frame of the centrifugal in any suitable manner, said torque motor having a pinion 61 engageable with rack 62, said rack being pivotally mounted at 63 to arm 64 of the double arm operating member 65. Said double arm member has a hooked arm 66 cooperable with and loosely contacted by roller 67 mounted on the hand operating arm 68. In Fig. 6, the torque motor is shown in full lines in a brake applied position wherein the brak shaft 30 has been rotated to apply the brake, the hand operating arm 68 being in its normal brake-off position. Handle 69 may be provided for moving hand operating arm 68. Sector 70 with cam 71 depending from its lower face is rotatable with the hand operating arm 68 to operate roller 72 on switch 73 when the hand operating arm is turned. As can be seen in the dot-dash lines, when the brake is set by hand, the contact point of roller 67 with surface 66' will have passed the dead center line B-B which is perpendicular to surface 66 and intersects the center 72' of pivot 72. Thus, the brake, when hand operated, will be held in a brake-on position, the torque motor, when deactivated, normally tending to turn the arm 64 in a clockwise direction and thus urging the roller 67 against the hook of arm 66.

From the preceding description, it is apparent that either a torque motor or an air cylinder can be used in conjunction with the same hand setting lever arrangement. When the brake is set by hand, the automatic control apparatus is interrupted and the hand lever will remain in set position. Under automatic operation by the air cylinder or the torque motor, the hand operated mechanism is not affected inasmuch as the hand operated arm is loosely contactable with the arm on the brake operating shaft.

In Fig. 8 is shown one form of wiring diagram which may be used in conjunction with the automatic cycle control and brake setting apparatus of the present invention, it being understood that other controlled operations may be included, such as the syrup separator control. The main power feed lines are indicated at with the main driving motor at 20. Control transformer 102 is connected across the power lines to supply energy at reduced voltage to the control bus leads 103 and 10 4. Switch 105, connecting bus 103 with the automatic cycle control buses 106 and 107, is normally closed and performs the function of switch 59 (Fig. 3) or switch 73 (Fig. 7) previously described.

When the emergency or hand lever is operated to set the brake, switch 105 is opened by operation of the cam on the hand lever so as to interrupt the supply of energy to the automatic cycle control buses 106 and 107-which will cause the control apparatus to reset and will stop the power supply to the drivingmotor if the hand brake is applied at the time power is being supplied thereto. In the event the hand brake is applied at a time when a braking system is operating, switch 108 which is connected to the brake motor solenoid 121 will have been closed previously thereby so as to prevent an opening of switch 105 by the hand lever from affecting the control circuit until the cycle has reached the point where the brake motor is de-energized. Brake motor relay solenoid 121 upon energizationin a manner to be described hereafter serving to close switch contacts 12111, b and c.

In the automatic control circuit about to be described, a start or run button may be pressed which will connect the centrifugal driving motor low speed windings to the power source. At this same time, the process timer and control timer are started in operation.

Various types of timers may be used and various arrangements thereof made. In the preferred form, a composite unit type, such 'as one knownas the Multiflex, may be employed, such a timer being diagrammatically illustrated in Figs. 9 and 10 and shown in U. S. Patent No. 2,175,864. It is to be understood that special timers or time delay switches of various kinds may be used for each of the timing devices. The Multiflexf timer need not-be described in detail except to point out that in the form shown in Fig. 9 four switches are used, and that in Fig. 10, four switches are used. The timers have their own motivating mechanism and clutch for engaging the mechanism with the switch operators. Each of the contacts or circuits can be set by adjustment of the on detent or off detent with respect to the timing scale indicated on the face of the timer so that the timing action or circuit closing will occur at any desired interval according'to the setting of the on detent and will be terminated at any desired interval with relation to the time started. If the on detentis above the upper limit of the scale, the corresponding switch is closed when the timer is started or energized. If the oif detent is below the lower limit of the scale, its corresponding switch, after having been closed according to the setting of the on detent, will stay closed until the timer is de-energiZed or reset.

The control timer operates to time the acceleration on low speed and the transfer to the high speed winding of the motor at the end of a predetermined time; When this occurs, the cycle timer stops but does not reset inasmuch as the clutch is maintained in an energized condition.

The process timer times the running time of the basket at high speed. In the event a coasting control is used, such as described in detail in'copending application Serial No. 756,307, filed June 21, 1947, now Patent No. 2,551,838, the process timer operates to open the coasting control switch so as to cut ofi the power supply to the high speed windings at the appropriate time. The process timer, by cutting off the high speed winding, also is employed to put the motor back on the low speed windings for regenerative braking and, at the same time, restarts the control timer. The control timer then times the regenerative braking period and thereafter applies the mechanical brake. Upon completion of these operations, the washing and discharging operations may be performed by manipulation of appropriate switches or push buttons.

As is well known in the art, a solenoid can be used to operate a plunger, said plunger being mechanically connected to any number of switch operators. In the accom panying drawings, the mechanical connection is omitted in the interest of clarity, the switches operated by a solenoid being given the same numeral with appropriate subscripts. The switches operated by the process timer and control timer will be designated by PT and CT, respectively, with distinguishing subscripts. When a solenoid is de-energized, certain of the switches may be closed andothers open. The legend below Figure 8 shows the symbols Cir 6 indicating whether a switch is normally open or closed when thesolenoid therefor is deenergized. t 1

Referring now to Fig. 8 in detail, the hand brake lever is assumed to be in a brake-on position. It is first released so as to allow closing of switch 105. Normally closed reset button 109 may be opened by depressing the same momentarily and allowed to reclose before the automatic cycle is started so as to reset all of the timers. Start button 110 is depressed when it is desired to start the cycle of operations, switch 10? being closed, start button 110 energizing solenoid 111 to close holding switch contact 111a operated by solenoid 111.

The low speed windings of the main driving. motor will be energized due to energization of low speed solenoid 112, said solenoidbeing connected to and closing power supply switch contacts 1120, 112d and 112.9 so as to connect the main drive low speed windings with the power supply 100. Y

The process timer clutch solenoid'lliiwill be' energize'd as will also the process timer motor 114, switch PTo of the process timer being normally closed at the beginning of the cycle. The solenoid 113 is connected to a clutch operator. A process timer is illustrated in Figure 10.

Control timer clutch solenoid 115 also will be energized as will be motor 116, a circuit being completed between bus 167 and bus 104 to the motor inasmuch as switch contact 112a connected to solenoid 112 was closed when the low speed solenoid 112 was energized. A control timer is illustrated in Figure9. At the end of a predetermined time of acceleration at low speed, the contacts CT1 will close and then a circuit can be completed to the high speed winding relay 117 through switch contacts 118a, switch contacts 118a having been closed by solenoid 118 upon the start of the cycle inasmuch as solenoid 118 was energized through normally closed switch PTz. Brake cooling'water'solenoid 119 also will be energized. Immediately after, or at the time, CTi closes, switch CTz will be opened by the control'timer which will open the circuit to the low speed winding inasmuch as switch'contacts 11% connected to solenoid 118 were previously opened by the energization of relay 118. Opening of low speed solenoid 112 will allow normally closed switch 112]] to close, thereby completing the circuit tothe high speed solenoid 117 which will close the connected high speed switch contacts 1170, 117d, 117e, 1171 and 117g to connect the motor for high speed operation. The low speed switch contacts 1120, 112d and 112a were opened when low speed solenoid 112 became tie-energized, the switch operators of solenoid 112 being so constructed.

If a coasting control is used so that the power supply to the motor is to be cut at the end of a predetermined time, or when the motor has attained a desired speed, the process timer, which is operating, will open switch IP'l'r. This will de-energize the high speed solenoid 117 so as to interrupt the source of energy being supplied to the main driving motor 20. It is to be understood that the coasting control does not necessarily have to be employed in the practice of the present invention, the process timer interrupting the high speed winding connection to the source of power after centrifuging has been completed.

During the coasting period or during the, accelerating and running period, the process timer can close switch PT3 to energize the wash water solenoid valve WWSV (Fig. 1) which will cause water to be sprayed on the walled sugar in the centrifugal basket. After a predetermined interval of time and before the braking starts, switch PT3 can be set to open so as to cut off the wash Water.

At a predetermined time interval, process timer contacts PTz will be opened to de-energize relay 118 which will open switch contacts 118a to interrupt the supply of energy to the high speed solenoid. 117. Openingofcontacts118a also will turn off the energy to the brake cooling water solenoid 119, the brake cooling water solenoid 119 having been previously energized to admit water to the brake drum for the purpose and in the manner disclosed in the Roberts Patent No. Re. 22,686.

Contacts 1153b will be reclosed inasmuch as solenoid 118 has been de-energized, thus again connecting the low speed winding to the power source for the purpose of regenerative braking. Switch contacts 117a, which were opened upon energization of 117, will reclose when the low speed solenoid is again connected across the line and contacts 112a will reclose to again start the control timer from its previously stopped position.

The regenerative braking will continue for a predetermined time until switch contacts CT3 close to energize solenoid 121i. Energization of solenoid 120 will open normally closed switch contacts 120a so as to disconnect the driving motor from the power supply and thus will stop the regenerative braking.

Normally open switch contacts 12% also are closed at this time to energize the brake motor control solenoid 121, solenoid 121 being connected with switches 121a, b and c. Energization of the brake motor control solenoid 121 will close switches 121a, 1211: and 1210 to energize the torque brake motor or a solenoid to control the air cylinder, said torque motor and air cylinder having been previously described. In Figure 2 can be seen schematically an air control valve 47A controlling air from line 47B, said air control valve being operable by the solenoid which is controlled by switches 121a, b, c. The brake control may take the form of a torque motor, shown in Figs. 6 and 7, or a solenoid controlling the air pressure to the air cylinder brake operator of Figs. 2 to 4, inclusive. The control timer motor 116 is stopped when the low speed solenoid 112 is opened at the end of regenerative braking by the opening of contacts 112a, the motor of the process timer continuing to operate. At the end of the maximum time for the process timer, contacts PTo will open so as to stop the motor. This will also deenergize the mechanical brake solenoid 121 so as to release the mechanical brake, thereby preventing overheating of the brake motor or the brake control solenoid.

in further operation of the device, the plow or jog button 122 may be momentarily depressed after the reset button has been pushed to de-energize solenoid 111 and therefore allow switch 111b to close, for removing sugar from the basket after the discharger plow is lowered therein, switch 111]; having been opened by the energization of solenoid 111. This will cause energization of solenoid 123 to close switch contactors 123a, 1231) and 1230 to the low speed winding of the motor through resistors, the resistor being selected to give, for example, approximately 100 R. P. M. of the motor. The rotation continues as long as the plow push button is depressed. This circuit is inoperative when the automatic cycle is operated because solenoid 111 maintains contacts 111b open. The jog button also can not be effective when the high speed solenoid 117 is energized because switch contacts 11711 are open. When the jog solenoid 123 is energized, switch contact 1235! will open as a safety feature to further prevent the possibility of having the low and high speed windings connected to the power source at the same time.

An example of one type of suitable operating cycle is seen in the chart of Fig. 11 wherein a scale of minutes is indicated in relation to the various operations for bringing a poly-phase induction motor having a synchronous speed of 1800 R. P. M. up to 1500 R. P. M. Other speeds may be chosen and other intervals employed, the cycle shown being merely illustrative of one type of a fast sugar centrifuging cycle. The coasting control also can be omitted.

The diagrammatic illustrations of the control timer and process timer seen in Figs. 9 and 10 show the various switches set for the cycle illustrated in Fig. 11. Assuming that the start button has just been operated following a loading of the centrifugal basket wherein the motor may be turning at about 200 R. P. M., a period of 10 seconds is allowed before the motor windings are shifted from low to high speed, it being assumed that the motor will reach a speed of about 450 R. P. M. during the 10 seconds period. The on detent of switch CTi of Fig. 9 is shown as being set for 10 seconds after the start of the cycle. At this time, switch CTz opens to complete the shift to the high speed winding. At the end of about 40 seconds after the shift to the high speed winding seconds after the start of the cycle), the motor will have reached the desired speed of 1500 R. P. M. Coasting switch PTi which is set to operate 50 seconds after the start will interrupt the driving action by opening so as to de-energize the motor and allow the centrifugal and motor to coast. If the coasting control is omitted, switch PTi may be eliminated. It is to be understood that the time for reaching the various speeds will depend upon size of motor, characteristics thereof, weight of charge in the centrifugal, and other variables.

The motor can coast for about 30 seconds, and during this period switch PTa may be turned on and off for the purpose of providing wash water to the centrifugal. At the end of the coasting period of 30 seconds, regenerative braking is started when PTz opens. This can continue for about 10 seconds. When CTz was opened previously in the shift from low to high speed winding, the control timer was stopped. When PTz opens to start regenerative braking, the control timer is again started. CTa will be opened 10 seconds after it has restarted so as to shut off the regenerative braking and set the automatic mechanical brake. In each of the timers, the first switch is set so that it will turn off approximately 5 seconds before the end of the range of the control timer, the purpose thereof being to de-energize the timers so that they will not remain on indeterminately.

When the hand brake lever is set, the source of power to the control apparatus will be interrupted so that the control will be reset and further operation of the centrifugal interrupted.

It is to be understood that the illustrated embodiments of the combination and details thereof may be varied without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. In a cyclically operated centrifugal machine including a basket carrying spindle, a rotary drive for the spindle, and a mechanical brake including a drum connected for rotation with said spindle and brake band means movable against said drum to decelerate the spindle, said brake including a brake-arm connected with said band means and movable to dispose the same in brake-on and brake-off positions, yieldable means normally acting upon said brake-arm with a predetermined brake unsetting force to bias the arm and band means to brake-01f position, power operated means for applying a predetermined brake setting force to said arm in a direction opposite to the brake unsetting force, a manually operable brake setting lever movable between an idle position and a brake setting position, said lever normally being unconnected with said arm and said band means so as to remain inactive upon movement of said arm and said band means by said power operated means, coacting means connected respectively with said lever and said brake-arm responsive to movement of said lever away from its idle position to overcome said brake unsetting force and shift said arm to its brake-on position independently of said power operated means, said coacting means comprising a lateral extension on said aim and a cam member connected with said lever and movable against said extension by movement of said lever to thrust said arm to brake-on position.

2. In a cyclically operated centrifugal machine including a basket carrying spindle, a rotary drive for the spindle, and a mechanical brake including a drum connected for rotation with said spindle and brake band means movable against said drum to decelerate the spindle, said brake including a brake-arm connected with said band means and movable to dispose the same in brake-on and brake-oft positions, yieldable means normally acting upon said brake-arm with a predetermined brake unsetting force to bias the arm and band means to brakeoii position, power operated means for applying a predetermined brake setting force to said arm in a direction opposite to the brake unsetting force, a manually operable brake setting lever movable between an idle position and a brake setting position, said lever normally being unconnected with said arm and said band means so as to remain inactive upon movement of said arm and said band means by said power operated means, coacting means connected respectively with said lever and said brake-arm and responsive to movement of said lever away from its idle position to overcome said brake unsetting force and shift said arm to its brake-on position independently of said power operated means, said coacting means comprising a lateral extension on said arm and a cam member connected with said lever and movable against said extension by movement of said lever to thrust said arm to brake-on position, said lever and cam member being rockable on a fixed axis from an idle position in which the line of pressure between said cam member and said extension lies between said fixed axis and the axis of said arm, to a locking position in which such line lies on on a side of said fixed axis away from said arm axis.

3. In a cyclically operated centrifugal machine including a basket carrying spindle, a rotary drive for the spindle, and a mechanical brake including a drum connected for rotation with said spindle and brake band means movable against said drum to decelerate the spindle, said brake including a brake-arm connected with said band means and movable to dispose the same in brake-on and brake-E positions, yieldable means normally acting upon said brake-arm with a predetermined brake unsetting force to bias the arm and band means to brake-off position, power operated means for applying a predetermined brake setting force to said arm in a direction opposite to the brake unsetting force, a manually operable brake setting lever movable between an idle position and a brake setting position, said lever normally being unconnected with said arm and said band means so as to remain inactive upon movement of said arm and said band means by said power operated means, coacting means connected respectively with said lever and said brake-arm and responsive to movement of said lever away from its idle position to overcome said brake unsetting force and shift said arm to its brake-on position independently of said power operated means, said coacting means comprising a lateral extension on said arm and a cam member connected with said lever and movable against said extension by movement of said lever to thrust said arm to brake-on position, and said power operated means comprising a fluid pressure operated cylinder containing a piston pivotally connected with said arm, and said yieldable means comprising a spring bearing against said piston to bias it and said arm to brake-off position.

4. In a cyclically operated centrifugal machine including a basket carrying spindle, a rotary drive for the spindle, and a mechanical brake including a drum connected for rotation with said spindle and brake band means movable against said drum to decelerate the spindle, said brake including a brake-arm connected with said band means and movable to dispose the same in brake-on and brake-01f positions, yieldable means normally acting upon said brake-arm with a predetermined brake unsetting force to bias the arm and band means to brake-off position, power operated means for applying a predetermined brake setting force to said arm in a direction opposite to the brake unsetting force, a manually operable brake setting lever movable between an idle position and a brake setting position, said lever normally being unconnected with said arm and said band means so as to remain inactive upon movement of said arm and said band means by said power operated means, coacting means connected respectively with said lever and said brake-arm and responsive to movement of said lever away from its idle position to overcome said brake unsetting force and shift said arm to its brake-0n position independently of said power operated means, said coacting means comprising a lateral extension on said arm and a cam member connected with said lever and movable against said extension by movement of said lever to thrust said arm to brake-on position, and said power operated means comprising a reversible torque motor having a driving connection with said arm, and means normally energizing said torque motor in reverse direction so that it also constitutes said yieldable means.

5. In a cyclically operated centrifugal machine including a basket carrying spindle, a rotary drive for the spindle, and a mechanical brake including a drum connected for rotation with said spindle and brake band means movable against said drum to decelerate the spindle, said brake including a brake-arm connected with said brake band means and movable to dispose the same in brake-on and brake-01f positions, yieldable means normally acting upon said brake-arm with a predetermined brake unsetting force to bias the arm and brake band means to brake-oft position, power operated means for applying a predetermined brake setting force to said arm in opposition to the brake unsetting force, a manually operable brake setting lever movable between an idle position and a brake setting position, said lever normally being uncon nected with said arm and said band means so as to remain inactive upon movement of said arm and said band means by said power operated means, coacting means connected respectively with said lever and said brake-arm and responsive to movement of said lever away from its idle position to overcome said brake unsetting force and shift said arm to its brake-0n position independently of said power operated means, said coacting means comprising a lateral extension on said arm and a cam member con nected with said lever and movable against said extension by movement of said lever to thrust said arm to brake-on position, and a stop element on said lateral extension in the path of movement of said cam member, said lever and cam member being rockable on a fixed axis from an idle position in which the line of pressure between said cam member and said extension lies between said fixed axis and the axis of said arm, to a locking position in which such line lies on a side of said fixed axis away from said arm axis and said cam member engages said stop element.

References Cited in the file of this patent UNITED STATES PATENTS 1,224,621 Fellmeth May 1, 1917 2,051,150 North Aug. 18, 1936 2,116,013 Carson May 3, 1938 2,127,305 Nabstedt Aug. 16, 1938 2,149,718 Anderson Mar. 7, 1939 2,229,013 Hoifman Ian. 14, 1941 2,371,857 Stevenson Mar. 20, 1945 

